During processing of semiconductor wafers it is conventional to carry out periodic in-situ cleaning of plasma etch and CVD reactors. U.S. Pat. No. 5,129,958 discloses a method for cleaning a CVD deposition chamber in a semiconductor wafer processing apparatus wherein fluorine residues in the chamber, left from a prior fluorine plasma cleaning step, are contacted with one or more reducing gases such as silane (SiH4), ammonia, hydrogen, phosphine (PH3), diborine (B2H6), and arsine (AsH3). Another technique for cleaning and conditioning interior surfaces of plasma CVD reactors is disclosed in commonly owned U.S. Pat. No. 5,647,953, the subject matter of which is hereby incorporated by reference. In the past these cleans were done with a wafer in the chamber to cover the electrode, but it has become more common to do waterless cleans.
Other techniques for cleaning plasma reaction chambers are disclosed in commonly owned U.S. Pat. No. 5,356,478; in U.S. Pat. Nos. 4,657,616; 4,786,352; 4,816,113; 4,842,683, 4,857,139; 5,006,192; 5,129,958; 5,158,644 and 5,207,836 and Japanese Laid-Open Patent Publication Nos. 57-201016; 61-250185, 62-214175, 63-267430 and 3-62520. For instance, in order to remove SiOx deposits, a fluorine-containing gas energized into a plasma has been used to clean interior surfaces of the chamber. Fluorine residues remaining after the reactor cleaning can be removed by passing a reducing gas such as hydrogen (H2), silane (SiH4), ammonia (NH4), phosphine (PH3), biborine (B2H6) or arsine (AsH3) through the reactor.
Chamber conditioning processes are also commonly used where a wafer is placed in the chamber to protect the electrode during conditioning. These conditioning processes are very common for deposition reactors following plasma cleans, and are also common for etch reactors following wet cleans. Sometimes the wafer has a deposited film on it which aids in the conditioning process. As an example, resist coated wafers have commonly been used to accelerate conditioning. Such conditioning steps may use process conditions without bottom electrode power to season the chamber walls.
A problem with using conditioning wafers season the plasma chamber to obtain reproducible process conditions when processing production wafers is that such conditioning wafers add cost and cause slowdown in production. Accordingly, it would be desirable for a conditioning treatment which is more economical in terms of cost and production efficients